I've wondered the same thing about the MD-80 and it's variants with 2+3 seating configuration, but just figured that the explaination must be so simple or fundamental that it would eventually come to me. It hasn't, and I give up.

O

Dassault Mercure: the plane that has Boeing and Airbus shaking in their boots.

OK....if you put a 200 lb person in each seat and figure out weights and moments, you determine that the lateral CG shifts 3 inches off the centerline (to the side with 2 seats) because of the seat configuration.

This is negligible, and is not countered by "shifted baggage" or fuel.

I would wager that a lateral cg shifts several inches to either side of centerline throughout a flight, due to fuel shifting, pax movement, etc.

Left to right balance is just not that big of an issue when the moments are that close to a center line.... unless the difference is that drastic. Fwd and aft are the key and critical weight and balance figures with any aircraft. Besides, you can always kick in a little aileron trim to make up the differance.

"It's not the size of the dog in the fight, but the size of the fight in the dog"

I know some Avro RJ operators with a 2+3 seat config. It´s the same issue. No noticeable lateral imbalance which requires trimming with fuel or cargo. I don´t even think that it requires extra aileron trim.

Just keep in mind that in case of a fuel imbalance the applicable warning is given at an imbalance of a few (I don´t have actual values at the moment) hundred kilos. Before that it might not affect the aircraft handling in a dangerous matter.

Quoting Troubleshooter (Reply 9):Just keep in mind that in case of a fuel imbalance the applicable warning is given at an imbalance of a few (I don´t have actual values at the moment) hundred kilos. Before that it might not affect the aircraft handling in a dangerous matter.

800 lbs in the ERJ-145

There are 3 types of people in this world, those that can count, and those that can't.

I've never had to use aileron trim in this airplane. In addition, the galley equipment is all on the right side of the aircraft, and most of the bags are loaded toward the right side since the door for the rampers to get in and out of is to the left. On the other hand, the APU does burn fuel out of the right side fuel tank, so it's not uncommon to take off with 100 lbs or so more fuel in the left than the right.

Still, when you're talking about a 50,000 lb airplane, having the CG a couple of inches off centerline doesn't make a noticeable difference.

As an Embraer captain in the US with over 3300 hours of Embraer flight experience. I can attest that balance along the lateral axis is never of concern. The slight misbalance from left to right can be easily overcome by a slight airleron trim input. As was stated earlier the max fuel imbalance is, I have flown aircraft with imbalances of upto 700 pounds with no adverse flight characteristics.

Quoting Mrocktor (Reply 15):Although literally speaking you are correct (as the axis the aircraft rolls around is longitudinal as you described), traditional aeronautical terminology is:

longitudinal axis = pitch
lateral axis = roll

That´s not correct! The movements along the three axes are as follows:
longitudinal axis = roll (controlled by the ailerons)
lateral axis = pitch (controlled by the elevator)
vertical axis = yaw (controlled by the rudder)